No abstract

A systematic account of fish species inhabiting waters surrounding the Desventuradas Islands, off Chile, is presented. The 61 species recognized belong to 33 families of Osteichthyes, and one of Chondrichthyes (Squalidae). It was found that the icthyofaunal links were stronger to the Western Pacific (90.7%) than to the Eastern Pacific (6.9%), despite the fact that these islands are much closer to the South American coast than to the coasts of Oceania. Hydrographic and physical barriers are postulated as explaining this pattern.

Aim We assessed the validity of the division of the Magellanic Province into the four provinces as proposed by Briggs & Bowen (J Biogeogr 39 12–30, 2012): Southern Chile, Tierra del Fuego, Southern Argentina and Falkland (Malvinas) Islands. We aimed to (a) present an updated list of the fishes from the region known as ‘Magellanic Province’, (b) analyse the specific richness of fishes in the Atlantic and Pacific sectors and their degree of endemism and (c) evaluate statistically the validity of the three Provinces proposed for the Atlantic sector. Location Southern tip of the American continent at latitudes higher than 40° S in the Atlantic as well as in the Pacific Oceans. Taxon 348 South American marine fish species. Methods The list of fishes was prepared by consulting more than 140 sources, many related to observations resulting from research cruises, although two ichthyological collections and two ichthyological websites were also used. The South American species with distributions extending outside of the area corresponding to the Magellanic Province, and all cosmopolitan species, were excluded of endemism analyses. For analysing fish distributions in the Atlantic sector, the data employed are from eight research cruises carried out from 1978 to 2006 from 37° to 55° south. A total of 523 fishing trawls have been analysed, grouped into cell of 1° × 1° cells. The species composition of each cell was evaluated by multivariate analysis (non‐metric multidimensional scaling, cluster and similarity analyses). Results The percentage of endemism in each sector (Atlantic 2.87% and Pacific 2.87%) is smaller than the endemism common to both sectors (9.2%). The total of endemic species in the Province is 14.94%, which is bigger than the 10% indicated as the lower limit for defining a biogeographic province suggested by Briggs (Marine Zoogeography, 1974). In addition, multivariate analyses do not show differences in the species composition, neither between Falkland (Malvinas) Islands and ‘Southern Argentina’ nor between the latter and Tierra del Fuego. Main conclusions The ichthyological data indicate only one biogeographic province in the region not four as previously posited.

We analyzed spatial, temporal, and age/sex variation in the diet of the South American sea lions (SASL, Otaria byronia) in southern Chile via δ13C and δ15N isotope analysis, with emphasis on exotic farmed and feral salmonids as a source of prey for this generalist predator. Isotope mixing models show that the primary prey consumed by SASL were demersal and benthopelagic fishes. Individuals sampled in summer and in the outer coast had higher δ15N values than those from winter or from the inner coast due to consumption of high trophic level demersal fish. We also found evidence of an ontogenetic shift in isotopic niche width as measured by δ13C and δ15N standard ellipse areas, with juveniles showing a restricted isotopic niche width (1.0‰2) in comparison to subadult (2.2‰2) and adult males (1.9‰2). The proportion of salmonids in the diet of the SASL was negligible and lower than reported in previous studies, which may be related to a recent drop in the production of salmon aquaculture in the region. Our study suggests that the SASL are able to adapt to shifts in spatiotemporal variations in the abundance of potential prey, including feral and farmed salmonids.

The "robalo" Eleginops maclovinus (Valenciennes 1830) is a common fish in the littoral, estuaries and rivers (under tidal effects zone) of southern South America, including the Falkland islands. The feeding habits of this species is known mainly in the two first mentioned habitats, where it consumes mostly animals from marine and estuarine origin. However, little is known about its seasonal feeding habits in limnetic environments. It is only assumed that it has to eat preys from freshwater origin. In the present study, 27 specimens of E. maclovinus were analysed, 9 of which had stomach contents. The zoophagic tendency of the species is corroborated, but also animals from low salinities and limnetic salinities were found to be consumed in the freshwater environment. Consequently, E. maclovinus appears as an extraordinarily versatile species, in relation to its feeding capacities, with physiologic characteristics allowing a wide osmoregulatory spectrum at the digestive level, probably one of the most variable within the suborder Notothenioidei, which has strong Antarctic links.Keywords: Feeding, seasonality, Eleginopsidae, physiological versatility, Chile. RESUMENEl "robalo" Eleginops maclovinus (Valenciennes 1830) es una especie de pez común en el litoral, estuarios y ríos (bajo efectos de mareas) en el sur de Sudamérica, incluyendo las Islas Malvinas. Sus hábitos alimentarios son conocidos en los dos primeros ambientes mencionados, donde consume principalmente animales de origen marino y estuarial. Sin embargo, poco o nada se sabe sobre su alimentación estacional en aguas dulces, salvo la suposición que allí debe comer presas de origen dulceacuícola. En el presente estudio se analizaron 27 ejemplares de E. maclovinus, de los cuales 9 tuvieron contenido estomacal. Se ha corroborado su tendencia zoofágica, pues en el contenido estomacal se encontraron animales de salinidades bajas y limnéticas, que fueron consumidos en aguas dulces. Así, E. maclovinus aparece como una especie extraordinariamente versátil en cuanto a sus capacidades alimentarias, con una fisiología que le permite aceptar un amplio espectro osmorregulatorio a nivel digestivo, probablemente uno de los más variables dentro del suborden Notothenioidei, de supuesto origen antártico.Palabras claVE: Alimentación, estacionalidad, Eleginopsidae, versatilidad fisiológica, Chile.